RAID 0 (striping) yields very little performance increase on basic apps, media play back, frames per a second, gaming, and any other basic usage like web browsing. It only increases data through put. So if you were dealing with very large files and constantly opening them and modifying them, or doing something like rendering or loading raw video onto your PC you will not see any performance increase.
You are better off just buying the faster hard disk in the first place and then have multiple for back ups.
Your largest bottle neck in any computer is always going to be disk I/O and really it only matters when the machine in question is doing so many tasks at once virtual memory access is slowing it down.
So, unless you are doing specific things on your computer a stripped RAID won't do you any good and you run the risk of losing data. In your case you did a RAID 0 + 1 so you have a mirrored stripped set, but even then you already lose a bit of performance on your RAID since it is mirrored.
I suggest you just buy the fast 10k RPM drives to begin with to run your OS and Apps, and then get a large regular SATA drive for storage and data files.
